Use 4-bpp colors from CGRAM

src/snes/ppu/render.rs

@@ -5,6 +5,14 @@ impl<TRenderer> PPU<TRenderer>
 where
     TRenderer: Renderer,
 {
+    fn cgram_to_color(&self, addr: u8) -> Color {
+        let entry = self.cgram[addr as usize];
+        (
+            (((entry >> 0) & 0x1F) as u8) << 3,  // Red, 5-bit
+            (((entry >> 5) & 0x1F) as u8) << 3,  // Green, 5-bit
+            (((entry >> 10) & 0x1F) as u8) << 3, // Blue, 5-bit
+        )
+    }
     pub fn render_scanline(&mut self, scanline: usize) {
         let mut line_idx: [u8; SCREEN_WIDTH] = [0; SCREEN_WIDTH];
         let mut line_paletted: [Color; SCREEN_WIDTH] = [(0, 0, 0); SCREEN_WIDTH];
@@ -15,14 +23,21 @@ where
             let ty = scanline % 8;
 
             for tx in 0..8 {
+                let palette = (entry.palettenr() * 4);
                 let c = chr.get_coloridx(tx, ty);
+                let color = self.cgram_to_color(palette + c);
                 line_idx[x + tx] = c;
-                line_paletted[x + tx] = (70 * c, 70 * c, 70 * c);
+                line_paletted[x + tx] = color;
             }
         }
 
         for (x, p) in line_paletted.into_iter().enumerate() {
-            self.renderer.set_pixel(x, scanline, p);
+            if line_idx[x] == 0 {
+                // Use main backdrop color
+                self.renderer.set_pixel(x, scanline, self.cgram_to_color(0));
+            } else {
+                self.renderer.set_pixel(x, scanline, p);
+            }
         }
     }
 }